RESUMO
Oncocytic carcinoma of the breast is rare and its molecular profiles remain poorly understood. MicroRNAs (miRNAs/miRs) have been identified as contributors to carcinogenesis at the post-transcriptional level; thus, an aberrant expression of miRNAs has attracted attention as a potential biomarker of numerous diseases, including cancer. The present study reports the case of a 76-year-old woman diagnosed with oncocytic carcinoma of the breast. Considering the distinctive feature of oncocytic carcinoma of the breast, which is the presence of granular eosinophilic cytoplasm containing numerous mitochondria, the present study hypothesized that the expression of mitochondria-related miRNAs could be altered in oncocytic carcinomas. Aberrant expression levels of the miRNAs previously reported as mitochondria-related miRNAs, such as miR-221-3p, -146a-5p and -16-5p, were revealed in tissue from specimens of oncocytic carcinoma of the breast, compared with that of a more typical type of invasive ductal carcinoma of the breast. The present study highlights the changes in miRNA expression in oncocytic carcinoma of the breast, suggesting its potential as a biomarker for diagnosis.